Dual-density EVA footwear mid-sole and method for making same

ABSTRACT

The method for fabricating a dual-density mid-sole includes the steps of: injection molding EVA material of a first density into a block; placing the first density EVA block and raw EVA material pellets of a second density together in a mold cavity; and applying heat and pressure to the first density EVA block and raw EVA material pellets of a second density in the mold cavity to form a fused component. The fused component is shaped and detailed into the mid-sole in a separate mold cavity. The result is a dual-density mid-sole consisting of one or more blocks of EVA material of a first density fused to EVA material of a second density where the size, shape and location of the different density sections can be accurately controlled and precisely defined. An article of footwear including an upper, the dual-density mid-sole consisting of one or more blocks of EVA material of a first density fused to EVA material of a second density, and an outsole, may be formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to footwear and to a method for makingfootwear and more particularly to a dual-density EVA footwear mid-soleand a method for making same.

2. Description of Prior Art Including Information Disclosed under 37 Cfr1.97 and 1.98

Footwear mid-soles fabricated from ethylene-vinyl acetate (EVA) materialare known in the art. Methods of fabricating EVA mid-soles are alsoknown. Such methods normally include heating and applying pressure toraw EVA material in a mold cavity to fuse the material into the desiredshape. After the component is removed from the mold and cured, it isshaped further and the exterior is detailed. The mid-sole is thenincorporated into the footwear product using conventional fabricationtechniques.

Fabrication of the EVA mid-sole in this fashion results in a mid-solewith a substantially uniform hardness throughout. However, for certainapplications, it has been found to be desirable to have an EVA mid-solethat is less hard in some areas, such as the forefoot, and harder inother areas, such as the heel.

The conventional method to provide an EVA mid-sole with areas ofdifferent hardness is to introduce the two different density raw EVAmaterials into different locations within the mold cavity and then fusethe different density raw EVA materials together to form the mid-sole ina single step by applying heat and pressure.

For example, raw EVA material of a first (relatively low) density isused in sections of the mid-sole where less hardness is desired and araw EVA material of second (relatively high) density is used in thesections where greater hardness is required. Each of the differentdensity raw EVA materials is introduced in a mold cavity in the form ofpellets that are poured into the respective desired locations in themold cavity. Heat and pressure is applied to the different density rawEVA materials in the mold cavity. This causes the pellets to fuse andform the mid-sole in a single molding step.

While this single step molding process results in a mid-sole withsections of different hardness due to the different densities of the rawEVA materials, the boundaries of the different density sections are notwell defined and are difficult to control. This is because the differentdensity raw EVA pellets tend to mix together to some extent as they arepoured into the mold cavity. The result is that the different densitysections tend to run into each other. Further, the different densitysections are not uniform in size and shape from one mid-sole to another.

It is therefore a prime object of the present invention to provide amethod of fabricating dual-density EVA footwear mid-soles with welldefined, stable different density sections.

It is another object of the present invention to provide method offabricating dual-density EVA footwear mid-soles with different densitysections of the desired size and shape.

It is another object of the present invention to provide a method offabricating dual-density EVA footwear mid-soles in which the size, shapeand location of the different density sections can be accuratelycontrolled.

It is another object of the present invention to provide a method offabricating dual-density EVA footwear mid-soles which are uniform instructure.

It is another object of the present invention to provide a method offabricating dual-density EVA footwear mid-soles using a two-step processwhere each mid-sole has harder and less hard sections of precisely thedesired shape, size and location.

It is another object of the present invention to provide a method forfabricating a footwear mid-sole wherein one or more blocks of EVAmaterial of a first density are formed by injection molding andthereafter the blocks are fused with EVA material of a second density ina separate mold cavity by application of heat and pressure to form themid-sole.

It is another object of the present invention to provide a dual-densitymid-sole including one or more blocks of EVA material of a first densityfused to EVA material of a second density.

It is another object of the present invention to provide n article offootwear including an upper, a dual-density mid-sole comprising one ormore blocks of EVA material of a first density fused to EVA material ofa second density, and an outsole.

BRIEF SUMMARY OF THE INVENTION

In general, the above objects are achieved by the present inventionwhich includes a method for fabricating a dual-density mid-soleincluding the steps of: forming EVA material of a first density into ablock; placing the first density EVA block and raw EVA material of asecond density together; and applying heat and pressure to the block andraw EVA material to form a fused component of dual-density EVA.

Preferably, the raw EVA material of a second density is in the form ofpellets when placed together with the first density EVA block.

The step of forming a block of the first density EVA material includesinjection molding EVA material of a first density into a block. Theblock is then trimmed to the desired shape.

The method further includes the step of shaping the fused component intothe mid-sole. Thereafter, design details on the exterior surface of thecomponent are created. The steps of shaping and detailing the componentmay be combined into a single step.

The step of shaping and the step of detailing include the steps ofplacing the component in a mold cavity and applying heat and pressure tothe component.

Preferably, the first density EVA material has a lower density than thesecond density EVA material.

The raw EVA material of a second density is preferably in the form ofpellets.

The method further includes the step of measuring the amount of EVAmaterial of a second density placed together with the first density EVAblock. This may be achieved by measuring the amount of raw EVA materialof a second density placed in the mold cavity with the bock as afunction of the volume of the block.

The step of placing the first density EVA block and the raw EVA materialof a second density together includes placing the first density EVAblock in a mold cavity and pouring the raw EVA material of a seconddensity into the mold cavity.

The step of applying heat and pressure to the block and raw materialincludes applying heat and pressure to the block and raw material in themold cavity.

In accordance with another aspect of the present invention, a method isprovided for fabricating a dual-density mid-sole comprising the stepsof: injection molding EVA material of a first density into a block;placing the first density EVA block and raw EVA material pellets of asecond density together in a cavity; and applying heat and pressure tothe first density EVA block and raw EVA material pellets of a seconddensity in the cavity to form a fused component.

The method further includes the step of shaping the fused component intothe mid-sole.

In accordance with another aspect of the present invention, adual-density mid-sole is provided including a block of EVA material of afirst density fused to EVA material of a second density.

The EVA block is formed separately, before the EVA block and EVAmaterial are fused together.

In accordance with another aspect of the present invention, adual-density mid-sole is provided including first and second blocks ofEVA material of a first density fused to EVA material of a seconddensity.

The blocks are formed by injection molding, before the EVA material andblocks are fused together.

In accordance with another aspect of the present invention, an articleof footwear is provided including an upper, a dual-density mid-solecomprising a block of EVA material of a first density fused to EVAmaterial of a second density, and an outsole.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS

To these and to such other objects that may hereinafter appears, thepresent invention relates to a dual-density EVA footwear mid-sole and amethod for making same as described in detail in the followingspecification and recited in the annexed claims, taken together with theaccompanying drawings, in which like numerals refer to like parts and inwhich:

FIG. 1 is a perspective with of a footwear product with the dual-densitymid-sole of the present invention;

FIG. 2 is a side elevation view of the footwear product of FIG. 1;

FIG. 3 is an exploded view of the footwear product of FIG. 1 showing thecomponents thereof;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 showingan idealized view of the interior of the mid-sole;

FIG. 5 is a cross-sectional view take along line 5-5 of FIG. 4 showingan idealized view of the interior of the mid-sole;

FIG. 6 is an elevation view of the assembly of injection molded EVAblocks;

FIG. 7 is a perspective view of an EVA block of a first size and shape;

FIG. 8 is a perspective view of a an EVA block of a second size andshape;

FIG. 9 is a perspective view of a mold cavity showing the placement oftwo EVA blocks therein;

FIG. 10 is a perspective view of the mold cavity of FIG. 9 showing themeasured amount of raw EVA pellets being introduced into the cavityafter placement of the EVA blocks;

FIG. 11 is a perspective view of the mold cavity after the EVA pelletshave been introduced and before the application of heat and pressure;

FIG. 12 is perspective view of the mold cavity and contents as heat andpressure are being applied to fuse the EVA, including a cut-out portionshowing the EVA material;

FIG. 13 is a perspective view of the fused EVA component as it isremoved from the mold;

FIG. 14 is a perspective view of the fused EVA component shaping anddetailing mold; and

FIG. 15 is a perspective view of the completed dual-density EVAmid-sole.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate a typical footwear product, generallydesignated A, incorporating the dual-density EVA mid-sole of the presentinvention, generally designated B. The mid-sole B of the presentinvention can be formed in whatever shape and size that may beappropriate for footwear product A and with whatever exterior contoursand surface features desired. Accordingly, the particular mid-soledesign and footwear product style shown in the drawings should not beconsidered in any way as a limitation on the scope of the presentinvention but instead simply as a means of illustrating a typicalmid-sole B resulting from the fabrication process of the presentinvention and a typical footwear product A that might incorporate such amid-sole.

FIG. 3 shows the components of footwear product A in exploded form.Product A consists of an upper 10, an insole 12, mid-sole B and anoutsole 14. Upper 10, insole 12 and outsole 14 are all standardcomponents manufactured by any one of a number of well known fabricationmethods and assembled with mid-sole B to form product A usingconventional techniques.

In order to achieve the dual density mid-sole B of the presentinvention, as illustrated in the figures, a two step process isemployed. First, the blocks 16, 18 of one density EVA material areforming by injection molding. The EVA material from which the blocks 16,18 are formed is selected for example to form blocks that will be softerand more resilient than the EVA material that will eventually form theremainder of the mid-sole.

The term “block” as used herein is meant to be broadly construed toinclude any mass of material (such as the relatively low density EVA asdescribed in the preferred embodiment) having definite, well-definedboundaries which is formed (for example by injection molding) prior toand separately from the molding process that fuses the block with amaterial of different density (such as the higher density EVA pellets ofthe preferred embodiment) to form a component.

FIG. 6 illustrates the assembly of blocks 16, 18 after it has cooled andhas been removed from the injection molding machine. Blocks 16, 18 arestill connected together by the plastic stem 20 produced by the channelsin the injection mold through which the molten EVA flows.

After blocks 16, 18 are severed from stem 20 and trimmed as needed; theyappear as seen in FIGS. 7 and 8. Two different size and shaped blocks16, 18 are shown to illustrate that the blocks may be of anyappropriated size and shape. Further, more than one block may beincorporated into a single mid-sole, as shown in FIG. 9.

As seen in FIG. 9, one or more of the soft EVA blocks 16, 18 are placedin the mold cavity 22 of a forming/pressing machine 24. The blocks canbe positioned at any location within the cavity. As shown in FIG. 10,after the soft blocks are placed in cavity 22, a measured amount of rawEVA material pellets 26 is the poured into the cavity. The mold cavitythen appears as shown in FIG. 11.

The raw EVA pellets 26 introduced into the mold cavity are of adifferent density than the EVA material used to form the blocks. In thisexample, the EVA pellets 26 are made of less dense EVA material than theEVA material from which blocks 16, 18 are formed. Accordingly, the rawEVA pellets will form a harder, less resilient end product than theblocks. The amount of pellets introduced into the cavity is carefullymeasured in accordance with the volume of the cavity, using a setformula, such that the fused component, called a “cup” because of itsshape, will be approximately the size and shape of the desired mid-sole.

As illustrated in FIG. 12, after the mold is closed, heat and pressureis applied to fuse the EVA pellets 26 and the blocks 16, 18 into asingle component or cup 28, see FIG. 13. Cup 28 is roughly the size andshape of the mid-sole but requires some finishing. The cup is thenshaped and detailed in a second forming/pressing step which is performedin a different mold 30 to complete the dual-density mid-sole of thepresent invention, illustrated in FIG. 15.

FIGS. 4 and 5 are idealized illustrations of the internal structure ofthe mid-sole of the present invention. FIG. 4 is a longitudinalcross-section of the mid-sole showing the locations of blocks 16 and 18within the mid-sole. FIG. 5 is a lateral cross-section take through thefront portion of the mid-sole showing block 18.

These figures show that the blocks 16, 18, made of the softer, lessdense EVA material, are precisely located within the mid-sole andsubstantially maintain their original shape and size through the fusingprocess. The blocks are completely surrounded by the harder EVA materialformed from the more dense raw EVA pellets. The result is morecushioning for the foot in areas where the softer blocks are located andmore support for the foot in the areas where the harder EVA is located.

Although somewhat idealized because some melting of the exterior of theblocks may occur, FIGS. 4 and 5 show that the boundaries between thedifferent density EVA materials in the fused component are much morewell defined than would be possible in a single step molding processwhere raw EVA pellets of both densities are poured into different areasof a mold cavity and melted together.

It will now be appreciated that using the fabrication method of thepresent invention, the contours of two different densities of EVAmaterial in the mid-sole will match perfectly and the location of eachof the different density EVA materials within the mid-sole can beaccurately controlled to form a stable fused component with softer andharder sections of size, shape and location precisely as desired.

While only a single preferred embodiment of the present invention hasbeen disclosed for purposes of illustration, it is obvious that manymodifications and variations could be made thereto. It is intended tocover all of those modifications and variations which fall within thescope of the present invention, as defined by the following claims.

1. A method for fabricating a dual-density mid-sole comprising the stepsof: forming EVA material of a first density into a block; placing thefirst density EVA block and raw EVA material of a second densitytogether; and applying heat and pressure to the first density EVA blockand raw EVA material of a second density to form a fused component. 2.The method of claim 1 wherein the raw EVA material of a second densityis in the form of pellets when placed together with the first densityEVA block.
 3. The method of claim 1 wherein the step of forming a blockcomprises injection molding EVA material of a first density into ablock.
 4. The method of claim 1 further comprising the step of trimmingthe block.
 5. The method of claim 1 further comprising the step ofshaping the fused component into the mid-sole.
 6. The method of claim 1further comprising the step of creating design details on the exteriorsurface of the fused component.
 7. The method of claim 6 furthercomprising the step of shaping the fused component into the mid-sole. 8.The method of claim 7 wherein the step of shaping and the step ofdetailing are combined into a single step.
 9. The method of claim 7wherein the step of shaping and the step of detailing comprise the stepsof placing the fused component in a mold cavity and applying heat andpressure to the fused component.
 10. The method of claim 1 wherein thefirst density EVA material has a lower density than the second densityEVA material.
 11. The method of claim 1 wherein the raw EVA material ofa second density has a higher density than the first density EVAmaterial.
 12. The method of claim 1 further comprising the step ofmeasuring the amount of EVA material of a second density placed togetherwith the first density EVA block.
 13. The method of claim 12 wherein thestep of measuring comprises the step of measuring the amount of raw EVAmaterial of a second density placed in the mold cavity with the bock asa function of the volume of the block.
 14. The method of claim 1 whereinthe step of placing the first density EVA block and the raw EVA materialof a second density together comprises the step of placing the firstdensity EVA block in a mold cavity and pouring the raw EVA material of asecond density into the mold cavity.
 15. The method of claim 14 whereinthe step of applying heat and pressure to the block and raw materialcomprises the step of applying heat and pressure to the block and rawmaterial in the mold cavity.
 16. The method of claim 1 furthercomprising the step of introducing a second first density block prior toapplying heat and pressure to fuse the component.
 17. A method forfabricating a dual-density mid-sole comprising the steps of: injectionmolding EVA material of a first density into a block; placing the firstdensity EVA block and raw EVA material pellets of a second densitytogether in a cavity; and applying heat and pressure to the firstdensity EVA block and raw EVA material pellets of a second density inthe cavity to form a fused component.
 18. The method of claim 17 furthercomprising the step of shaping the fused component into the mid-sole.19. A dual-density mid-sole comprising a block of EVA material of afirst density fused to EVA material of a second density.
 20. Themid-sole of claim 19 wherein the EVA block is formed separately, beforethe EVA block and EVA material are fused together.
 21. A dual-densitymid-sole comprising first and second blocks of EVA material of a firstdensity fused to EVA material of a second density.
 22. The mid-sole ofclaim 21 wherein the blocks are formed by injection molding, before theEVA material and blocks are fused together.
 23. An article of footwearcomprising an upper, a dual-density mid-sole comprising a block of EVAmaterial of a first density fused to EVA material of a second density,and an outsole.